1. Field of the Invention
The present invention relates to a self-contained emergency battery charger. It is intended for use in systems in which a battery is used to start a motor.
2. Description of the Prior Art
Starter batteries often become sufficiently discharged so as to be unable to start a motor. This is often due to lights or other accessories being accidentally left on. Also, defective vehicle charging systems can result in the same problem.
Conventional methods of starting such a disabled vehicle include push-starting, using jumper cables and using conventional battery chargers. Both push-starting and jumper cables require the presence of another car. Furthermore, jumper cables are hazardous because, if improperly connected, they can lead to damage of the vehicle's electrical system. Also, an explosion of battery gases is possible.
The disadvantage of conventional battery chargers is the need to be near a source of external power such as 120 volts alternating current (VAC).
Several self-contained emergency battery chargers have been developed. These include U.S. Pat. No. 4,004,208 (Tamminen) and U.S. Pat. No. 4,540,929 (Binkley). Tamminen's device provides a slow recharge cycle, whereas Binkley's device offers only passive current regulation with a resistor. Binkley's device cannot deal with a short circuit or a severely discharged battery without excessive heating. Additionally, the rather large value of resistor that must be used in this scheme severely limits charging current as the vehicle's battery begins to come up in voltage.
Other devices in the art include those disclosed in U.S. Pat. Nos. 3,504,262 (Sada et al); 4,258,305 (Anglin) and 3,763,415 (Ownby). Their disadvantages are a need for an external source of power, insufficient portability or lengthy charging/recharging times.